Manufacture and treatment of organic materials comprising organic esters



Patented July 9, 1940 UNITED STATES MANUFACTURE AND TREATMENT OF OR- I GANIC MATERIALS COMPRISING ORGANIC ESTERS Henry Dreyfus, London, England No Drawing. Application January 13, 1938, Se-

rial No. 184,801. 1937 Claims.

This invention relates to the saponification of threads, fibres, yarns, fabrics, ribbons, films and like materials having a basis of cellulose acetate or other organic ester of cellulose.

It is difiicult to effect saponification, and particularly partial saponification of materials of the kind referred to above in such a .way that the products have desirable tensile properties and at the same time can be dyed uniformly with cotton 10 dyes without streakiness or similar defects.

I have now found that the desired results can readily be obtained by treating the materials in an alkaline saponifying bath formed by dissolving in an aqueous medium. two salts of a weak l6 polybasic acid with the same or different strong bases,' said salts containing different molecular proportions of the acid radicle. Thus, for example, the bath may be made from mixtures of trisodium or potassium phosphate with disodium or potassium phosphate, of sodium, potassium, calcium or barium sulphides with sodium, potassium, calcium or barium hydrosulphides, or of sodium or potassium carbonates with the corresponding bicarbonates. Preferably both salts 25 are of alkaline reaction. Salts of alkali metals are particularly suitable.

It is generally of advantage for the salt of lower acid radicle content to predominate considerably in the mixture. It may. for example, conveniently 80 be present to the extent of 5-10 or times the molecular proportion of the salt of higher acid radicle content. The concentration in which the salts are employed will depend on the nature of the materials treated, the degree of saponiflcation desired and the alkalinity of the salts, i. e..

' the pH value of aqueous solutions of given concentration. When treating ordinary cellulose acetate yarn, for example having an acetyl value of between 51 and 54 so as to effect a reduction in the acetyl content of between and the bath may contain an amount of trisodium phosphate ranging from that theoretically required to produce the desired saponification to twice the theoretical amount together with some 8-15% on the weight of the trisodium phosphate of disodium hydrogen phosphate, the bath volume being between :1 and 80:1, e. g., :1 or :1. Similar proportions are suitable when the corresponding potassium salts are used or when sodium carbonate is used in admixture with sodium bicarbonate. When sodium or potassium sulphide is used in conjunction with the corresponding hydrosulphide, the concentration should preferably be reduced, i. e., a. bath volume greater than 60:1 should be used. With the corresponding calcium salts, however, the concentration should preferably be considerably higher, that is the amount of salts used should be several times that theoretically required and in addition the bath volume may be reduced, for example to 30:1.

In Great Britain January 18,

The temperature of the bath may be relatively low, for example below 40 or 50 0., though it is preferable to carry out the saponification at considerably higher temperatures, for example from 60-80 C.

When the process is applied to materials which have been stretched considerably at some stage in their manufacture, for example in the course of a wet spinning operation or of a stretching operation carried out on threads after spinning while they are under the action of an organic swelling agent or of steam or of hot water, it is of advantage to use baths of higher concentration than would be used, other things being equal, in the treatment of ordinary unstretched threads of the same material. If, on the other hand, the threads treated have undergone a shrinking operation after stretching or without their having been stretched, low concentrations of the saponifying agent may be used.

The saponification may be carried out, on the materials in any suitable form, for example in hank form or wound on to perforated bobbins or other package carriers. On the other hand the materials may be drawn continuously through the saponifying. bath but as .the saponification baths of the invention are necessarilysomewhat slow in action, continuous operation does not in general present advantages over saponification in package form. ti The following examples illustrate the inven- Example 1 A bath is made up as described in Example 1, but using the following quantities for each 100 lbs. of yarn:

'irisodium phosphate lbs 100 Dlsodium hydrogen phosphate lbs 15 Water gallons 5800 The yarn is allowed to remain in the bath at -90 C. until 20-30% of the original acetyl 0011-1 tent is removed.

Though the invention has been described with particular reference to cellulose acetate materials, the process of the invention is also applicable to other organic esters of cellulose, for example cellulose formate, propionate, butyrate, mixed esters such as cellulose nitrate-acetate, nitrate-propionate, acetate-propionate, acetate-propionatenitrate and ether esters such as ethyl cellulose acetate and oxyethyl cellulose acetate.

The degree of saponification may be sufiicient to reduce the acidyl content of the ester by 15-20% or even' less. It is preferably somewhat higher however, for example sufiicient to reduce the acidyl content by 20-25 or 30%. Considerably higher degrees of saponification may be obtained, sufiicient to remove, for example 35 or 40-50% or even more of the acidyl content of the materials according to the particular purpose in view.

Having described my invention, what I desire to secure by Letters Patent is:

1. Process for the production of improved artificial materials, which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous bath containing two alkali metal salts of the same weak inorganic polybasic acid, one of said salts containing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts.

2. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous bath containing twosalts of the same alkali metal with the same weak inorganic polybasic acid, one of said salts containing a higher molecular proportion of acidradicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts.

3. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis'of organic ester of cellulose by treatment in an aqueous bath made by dissolving in an aqueous medium two salts of the same alkali metal with the same weak inorganic polybasic acid, one of said salts containing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts,

.the salt containing the lower molecular proportion of acid being present in excess.

4. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous bath made by dissolving in an aqueous medium two salts of the same alkali metal with the same weak inorganic polybasic acid, one of said salts contain ing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts, the salt containing the lower proportion of acid radicle being present in an amount ranging from that theoretically required to produce the desired saponification to twice that amount and the salt containing the lower proportions of acid radicle being present to the extent of 5 to 15 times the molecular proportion of the salt of higher acid radicle content.

the saponification of materials having a basis of 5. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous hath made by dissolving in an aqueous medium two salts of the same alkali metal with phosphoric acid, one of said salts containing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts, the salt containing the lower molecular proportion of acid being present in excess.

6. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous bath made by dissolving in an aqueous medium two salts of the same alkali metal with carbonic acid, one of said salts containing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts, the salt containing the lower molecular proportion of acid being present in excess.

'7. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous bath made by dissolving in an aqueous medium trisodium phosphate and disodium hydrogen phosphate, the trisodium phosphate being in excess and the bath being alkaline solely owing to hydrolysis of one of the salts.

8. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of organic ester of cellulose by treatment in an aqueous bath made by dissolving in an aqueous medium trisodium phosphate and disodium hydrogen phosphate, the trisodium phosphate being present in an amount ranging from that theoretically required to produce the desired saponification to twice that amount and the trisodium phosphate being present to the extent of 5 to 15 times the molecular proportion of the disodium hydrogen phosphate.

9. Process for the production of improved artificial materials, which comprises saponifying threads, fibres, yarns, fabrics, ribbons or like materials having a basis of cellulose acetate by treatment in an aqueous bath containing two alkali metal salts of the same weak inorganic polybasic acid, one of said salts containing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts.

10. Process for the production of improved artificial materials which comprises saponifying threads, fibres, yarns, fabrics. ribbons or like materials having a basis of cellulose acetate by treatment in an aqueous bath made by dissolving in an aqueous medium two salts of the same alkali metal with carbonic acid, one of said salts containing a higher molecular proportion of acid radicle than the other and the bath being alkaline owing solely to hydrolysis of at least one of said salts, the salt containing the lower molecular proportion of acid being present in excess.

HENRY DREYFUS. 

